Strange engine problem!

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leeve

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Hey guys,new to the this forum and im coming over from nitro.Ne ways i bought a used 5sc for $400.I bought a new stock 26cc engine and cant get it started.I did flood it a few times but cleared it all out. The only way i can start it is when i apply full throttle,but it revs up and dies.Now i checked spark and its good(even changed it out) but i find my prime bulb isnt filling up all the way and when i take the yellow line off it relieves pressure,is that normal? So i took both fuel lines off and put them back on and try to start,bulb fills up a bit but wont start.This time i take line the off and there is no pressure. Walbro 668 with stock settings.

Sorry for the book but im pulling out my hair,i though these were easier to start then nitro.
 
leeve said:
Hey guys,new to the this forum and im coming over from nitro.Ne ways i bought a used 5sc for $400.I bought a new stock 26cc engine and cant get it started.I did flood it a few times but cleared it all out. The only way i can start it is when i apply full throttle,but it revs up and dies.Now i checked spark and its good(even changed it out) but i find my prime bulb isnt filling up all the way and when i take the yellow line off it relieves pressure,is that normal? So i took both fuel lines off and put them back on and try to start,bulb fills up a bit but wont start.This time i take line the off and there is no pressure. Walbro 668 with stock settings.

Sorry for the book but im pulling out my hair,i though these were easier to start then nitro.
Click to expand...
Maybe you have the fuel lines on wrong way round?
Try swapping them and see what happens
 
Maybe try leaning the low speed needle so she wil start and stay started then richen it up until she sounds right. Sounds like you may be too rich. Stock settings are H- 1 3/8, L- 1 1/4 out from the closed position. Also so you know, you cant flood the engine pumping the bulb too much. I pump mine until I see no more air bubbles in the yellow tube. Plus the bulb don't fill all the way.
 
MonsterAir said:
Maybe try leaning the low speed needle so she wil start and stay started then richen it up until she sounds right. Sounds like you may be too rich. Stock settings are H- 1 3/8, L- 1 1/4 out from the closed position. Also so you know, you cant flood the engine pumping the bulb too much. I pump mine until I see no more air bubbles in the yellow tube. Plus the bulb don't fill all the way.
Click to expand...



I did try leaning it out a bit but it has the same result.I just bought a new carb because I think thats where my problem lies and I bought a rebuild kit fir it cause I like to see if I could fix it, im pretty sure it may be the diaphram letting in to much fuel.I also like to familiarize myself with it.
 
Straight from the HPI manual.

MonsterAir - I am not sure where you got that High needle -1 3/8 figure as a base setting, but it is wrong.
Base setting on the High needle is 1 1/2 turns out from all the way in.
Not that it would affect the running issue here, because the Low needle would affect the idle circuit.
Try reving the engine once it starts & hold the thing at a higher RPM for a while.
This way it will continue to clear the floods, and burn off any access fuel on the spark plug that could be causing your stall issue.
If you did flood it a few times, chances are you have ruined the spark plug, if the rev don't work.
Try a new plug, and see what happens.

Carb%20Settings_zpszt7fhtrt.webp
 

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Yes sir, but you always want to start at factory settings to start your tuning.

I have seen MANY that when running a pipe will actually go up to around 1 5/8 turns out on the High needle.

Very - Very seldom do you run that needle leaner, especially on a stock 668 carb.
In fact I have Never tuned any car learner than the 1 1/2 position with the 668 carb.
Others like the WT990 / and / WT813 are a slight bit different, and some have tuned lower.
BTW: I've had large scale cars since before the HPI come out, and have tuned literally hundreds over the Many years now.

I still have:
(5) HPI Baja Models
(2) FG MT models
(1) FG Comp. Baja
(1) MCD Gen 1 Baja1000
(1) Himoto Warrior / Redcat TT Buggy
(1) 1/4 scale QSAC race car
(1) Large Scale Air Boat
(7) Large Scale Boats
(1) Large Scale Pulling Tractor
... Probably missing something in that list too ... :w00t: :lol:
 
I just took the time to go search that up on DDM.
I guess all I can say is it is not good that they have put that incorrect information out there for people to find.
I have seen people lean seize an engine due to those exact settings.
You can find the 1 1/2- H 1 1/4-L base line on many sites, and including the HPI engine manual like I posted a picture of earlier.

http://zenoahmodifiedengines.com/how-to-tune-zenoah-engine.php

http://www.zenoah.co.jp/ddoc/ZENO/ZENO2009_AAen/ZENO2009_AAen_G230RC,G260RC_.pdf

Page 5 in the Zenoah manual.
Z%20Carb%20Settings_zpsftveyhin.webp

My biggest reason for making this point is, you will never see anyone trash an engine by running a bit to rich, but ... You certainly can by running it lean.
I've seen a few get trashed on the very first tank of fuel, and that makes for a Very unhappy / disappointed new person to the hobby.
It is always better to have good information, and learn the process of tuning from a person with plenty of exprience. ;)
 
Thanks for the info guys, I remember when I had my nitro mgt I thrashed one of my engines because they put 3 different carbs on over time and never updated the factory settings.I am going to pull apart this carb and try to rebuild it.I did order a new 668 and hopefully that will solve my problem because im itching so bad to drive this and I cant even get it started. I will update my progress as I go.
 
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